This invention relates to nozzles for rotary irrigation sprinklers, and more particularly to a new and improved nozzle construction for enhancing the close-in distribution of water ejected from such nozzles.
Rotary sprinklers have long been known and used in the irrigation art to apply irrigating water over a circular or part circular area around the sprinkler. Typically, such sprinklers employ single or multiple outlet nozzles though which water is ejected upwardly and radially outwardly from the sprinkler body, and include a means for causing the nozzle to be rotated such as by an impact drive arm assembly mounted to the sprinkler body which interrupts the stream from the nozzle, or by a water operated motor such as a ball drive, gear drive or turbine drive device mounted within a sprinkler casing forming part of the sprinkler body. In many cases, the sprinkler is designed to have a pop-up mechanism wherein the nozzle is attached to the upper end of a tubular riser mounted within the sprinkler casing for extension and retraction so that the nozzle will be extended above the casing when the sprinkler is in operation, and be retracted inside the casing when the sprinkler is not in operation.
The nozzles used with such sprinklers, particularly those of the pop-up type, frequently incorporate one or more nozzle outlets formed as tubular passageways surrounded by a housing coupled to the upper end of the riser, and which are designed to eject generally columnated water streams outwardly around the sprinkler. One example of such sprinkler and nozzle construction is that illustrated in U.S. Pat. No. 4,681,259 entitled Rotary Drive Sprinkler.
The function of the sprinkler nozzle is to convert the pressure energy of the relatively low velocity water entering the sprinkler casing from a supply source into kinetic stream energy. The more effective the conversion of the pressure energy to kinetic stream energy, the greater the distance the stream from the nozzle will travel before falling to the ground, the maximum distance for a given supply pressure being referred to in the art as the maximum range of the nozzle.
With irrigation sprinklers, it is generally recognized that the ideal distribution pattern of precipitation around the sprinkler body is a wedge shaped pattern with the maximum water precipitation rate or "fallout" occurring at the sprinkler body and decreasing progressively to zero radially outwardly away from the sprinkler. For this reason, most sprinklers are designed to be installed in an array with the spacing between adjacent sprinklers being equal to the maximum range of the nozzle employed. To reduce the number of sprinklers required to irrigate a given area, it would be desirable to employ nozzles having the greatest range possible. However, if all of the the incoming water pressure is converted to kinetic stream energy, the water ejected by the nozzle would produce a doughnut-shaped fallout pattern with little fallout occurring near the sprinkler body and relatively large fallout occurring toward the maximum range. Thus, to achieve the ideal precipitation pattern, some compromise in range must be made to achieve the desired fallout pattern close-in to the sprinkler body.
With rotary sprinklers of the impact drive type, this compromise is achieved, at least in large part, as a result of the repeated and cyclical stream interruptions of the drive arm. However, with continuous flow type nozzles such as of the type disclosed in the aforementioned patent, increasing the close in water precipitation pattern must be achieved through other means. One approach has been to use multiple nozzle passages, a relatively large passage for achieving the desired maximum range (typically referred to as a "range nozzle"), and a relatively smaller nozzle passage (typically referred to as a "spreader nozzle") for achieving more close in water fallout. With the multi-nozzle approach, the principal mechanism for achieving fallout at the desired range is that of air friction. That is, the decelerating effects of air friction act on the surface area while inertia is dependant on volume, so the ratio of inertia to friction increases with water droplet diameter. Since large size range nozzles produce relatively high velocity streams of relatively large sized water droplets, the effects of air friction are minimized as compared with the air friction effects on the relatively lower velocity, smaller droplet sized streams from the smaller size spreader nozzles.
In an effort to produce the desired wedge shaped precipitation pattern with multi-nozzle sprinklers, various proposals have been made for varying the geometry and size of the small spreader nozzle to enhance close-in water fallout. Small outlet openings or outlet openings with a large perimeter but a small area tend to produce small droplets that lose their kinetic energy rapidly and fallout close-in to the sprinkler, while larger outlet openings produce larger droplets which project much further. In an effort to achieve the substantial volume of small droplet size water required to achieve the ideal wedge shaped precipitation pattern, it has been necessary to utilize a number of small diameter outlet openings or spreader nozzles to compliment the larger diameter range nozzle. A major problem, however, with this approach is that the smaller the diameter of the outlet nozzle, the greater the risk that the nozzle opening will become clogged with debris such as sand, dirt, silt, and other particulate material frequently found in irrigation water supply systems, and such small size nozzles tend to produce mist-like sprays which are very susceptible to being blown by wind.
Thus, it would be desirable to provide the relatively large amounts of water needed to achieve the high precipitation rates required for close-in watering to produce a more ideal wedge shaped water distribution pattern without requiring the use of small size outlet nozzle openings. As will become more apparent hereinafter, the present invention has achieved this end in a novel yet highly reliable and effective manner.